I have a quite large zip file with archived documents and I want to add a new file into it.
How to do it quick and easy? The archive is quite large, so extract+add+compress+delete is not preffered option.
AFAIK There's no (free) onboard app to achieve this.
The easiest way would be to do it via command line.
zip /path/to/zipfile.zip file1 file2
If you want to add all(!) files within a directory and subdirectories, run
zip -r /path/to/zipfile.zip /path/to/dir
It will also add
.DS_Store files and that like, so be careful with the latter command.
However, if you're fine with spending some money, you could take a look at http://macitbetter.com. They provide an app called BetterZip 2 which is also capable of doing what you want.